Effect Of Cerium Oxide And Zirconium Oxide Doping On The Denitration Performance Of Cordierite Based CuO/Al₂O₃ Catalyst

Nitrogen oxides(NOx)is one of the major pollutants such as acid rain,fog haze and photochemical smog,which seriously affect the ecological environment,human health and the sustainable development of economy and society in China.Selective catalytic reduction(SCR)is the most effective technology for the removal of NOx.At present,the most mature SCR catalysts for commercial application at home and abroad are vanadium based catalysts,however the toxicity and carcinogenicity of V2O5 have been limited to its application.The honeycomb cordierite based CuO/Al2O3 catalyst is considered as a potential substitute for vanadium based SCR catalyst for its non-toxic,efficient,cheap and environmentally friendly advantages.However,the CuSO4 species generated by the active component Cu in the presence of SO2 are easily affected by the H2O in the flue gas,which reduces the denitrification activity and stability and so on.It is important to intensively study and improve the denitrification performance of the CuO/Al2O3 catalyst.The main research ideas and contents of this paper are as follows:aiming at the denitrification performance of honeycomb cordierite based CuO/Al2O3 catalyst,the cause of gradual inactivation in the reaction process was analyzed.Considering that adding auxiliary CeO2 to stabilize the active component copper,the effect of loading mode and loading amount of Cerium on the denitrification stability of the catalyst was studied.Considering that adding auxiliary Cerium-Zirconium solid solution to reduce the adsorption of water gas on the surface of the catalyst,the effect of Cerium-Zirconium solid solution on the denitrification stability of the catalyst was studied.The following conclusions are drawn:1.Because of the competitive adsorption of water vapor and NH3 in the flue gas environment,excessive water vapor affects the denitrification activity of the catalyst.With the increase of reaction time,low content of water vapor still causes catalyst deactivation.The key of inhibiting the deactivation of catalyst and improving the stability of denitrification is stabilizing active component Cu and reducing the adsorption of water vapor on catalyst surface.2.The loading mode of cerium has a certain effect on the denitrification activity and stability of honeycomb cordierite based CuO/Al2O3 catalyst.Distribution impregnation and co impregnation of Ceo2 will not improve denitrification activity and stability,while Al2O3 and CeO2 co-coating as carrier can improve denitrification stability.The catalyst for the optimal loading amount of cerium is Cu(1)/Ce(5.0)+Al(20),compared with the honeycomb cordierite based CuO/Al2O3 catalyst,its denitrification activity and stability are all obviously improved.3.The Al2O3 and CeO2 co-coating as carrier can not only enhances the interaction between CeO2 and Al2O3,but also tightly combines with Cu so that the active component copper can enter the crystal lattice of cerium to form a Ce-O-Cu solid solution,which reduces the exposure of the active component copper on the surface of the catalyst,and thus raises the denitrification stability.Raman and H2-TPR show that when the loading amount of CeO2 is 5%,the Raman signal of the Cu2+-O-Ce4+ on the CuO/Al2O3 catalyst surface can be increased to a maximum extent,thus improves the formation of oxygen vacancy and the ability of oxygen adsorption,which reduces the peak temperature of the H2-TPR,promotes the lattice oxygen migration and improves the denitrification activity,which is consistent with the denitrification performance.4.Cerium-Zirconium solid solution formed by cerium and zirconium doping can further improve the denitration performance of honeycomb cordierite based CuO/Al2O3 catalyst.The addition of Cerium-Zirconium solid solution enhances the interaction between CuSO4 and each component,maintains the high dispersion and valence distribution of Cu on the surface of the catalyst,improves the lattice oxygen fluidity in the solid solution,improves the catalyst' s ability of storing and releasing the surface reactive oxygen species,and the CuO is easy to oxidize and redox,greatly reduces the adsorption of water vapor on the surface of the catalyst,thus reducing the influence of the competitive adsorption of water vapor and NH3 and the influence of CuSO4 aggregation,finally makes the catalyst exhibits higher denitrification activity and stability of water resistance.5.The real active component of Cu(1)/Ce(5)+Zr(1.78)+Al(20)catalyst is still copper.